This invention relates generally to lubricants, and more particularly to lubricating oils having fluorocarbon particles dispersed therein for use in internal combustion engines to reduce the emission of pollutants into the atmosphere.
Even the most carefully finished metal surfaces have minute projections and depressions therein which introduce resistance when one surface is moved relative to another. The application of a lubricant to these surfaces reduces friction by interposing a film of oil therebetween. The rotation of a journal in a bearing draws the oil between it and the bearing so that the two metal surfaces are separated by a very thin film of oil. The degree of friction depends on the viscosity of the oil, the speed of rotation and the load on the journal. If the journal starts rotating after a period of rest, it may not drag enough oil to float the surfaces apart, hence friction will then be considerably greater, the friction being independent of the viscosity of the lubricant and being related only to the load and to the "oiliness" property of the residual lubricant to stick tightly to the metal surfaces. This condition is referred to as "boundary lubrication", for then the moving parts are separated by a film of only molecular thickness which may cause serious damage to the overheated bearing surfaces.
The two most significant characteristics of a hydrodynamic lubricant are its viscosity and its viscosity index; the latter being the relationship between viscosity and temperature. The higher the index the less viscosity will change with temperature. Lubricants serve not only to reduce friction, but also to remove heat developed within the machinery and as a protection against corrosion.
The role played by lubrication in the operation of an internal combustion engine has not been fully appreciated, for while there is widespread concern with deleterious pollutants emitted by vehicles employing such engines, expedients for reducing noxious emissions have not heretofore involved the nature of the engine lubricants.
In an internal combustion engine, the pollutants are constituted by oxides of nitrogen, unburned hydrocarbons and carbon monoxide. The ecological problems created by automobiles are not merely due to the emissions from the engine exhaust into the atmosphere, for the emitted substances produce chemical reactions in the atmosphere when radiant energy is supplied thereto by the sun. Thus photochemical smog, which is now encountered in many major cities, is the result of photochemical reactions involving hydrocarbons from exhaust gases, evaporation losses, and nitric oxide.
Some of the factors which are involved in the emission of pollutants will now be considered.